Official since 1957.
Over the 1000+ years of Hungary’s existence, under various goverments and royalties, there have been several flags. The current flag and official flag of Hungary (Magyarország zászlaja) since October 1, 1957 (after the 1956 Revolution) has three colors (red, white and green). Its design is based on national republican movements of the 18-19th century. The colors come out of the Middle Ages. From Wikipedia: The nation of Hungary originated from the national freedom movement from before 1848, which culminated in the Hungarian Revolution of 1848. The revolution was not only in opposition against the monarchy but also the Habsburg Empire, as well as to form an independent republic. Accordingly, the Hungarian flag features a tricolour element, which is based upon the French flag, as a reflection of the ideas of the French revolution; while red, white, and green are colours derived from the historical Hungarian coat of arms, which have essentially remained in the same form since the mid-15th century, with exception to some minor differences, and were marshalled from arms that first appeared in the late 12th and early 13th century as arms of the Árpáds, Hungary’s founding dynasty. The stripes are horizontal rather than vertical to prevent confusion with the Italian flag, which had also been designed after the French flag. According to other data, the recent form of the Hungarian tricolour had been already used from 1608 at the coronation of Mathias II of Hungary.